Prior methods for measuring those high-speed transmission electromagnetic waves, such as radar wave, light wave infrared ray, laser beam, etc., generally include two types: (1) Emitting HF electromagnetic wave or light wave in the form of a pulse, measuring the frequency value between the emission of a pulse and the counting by a counter of the return number of waves, and then converting the value into a time value; or to calculate the time value from the lightspot width indicated by a cathode ray oscillograph. This is known as "pulsed radar" method, and (2) using a given rate to alter the frequency of HF continuous wave, then comparing the frequency of the reflected signal with the frequency of the emission signal. This is known as "frequency-modulated continuous wave radar" method. However, since the speed of the light wave or electromagnetic wave is so quick (C=3.times.10.sup.8 M/sec.) that a UHF of 300-3,000 MHz or a SHF of 3,000-30,000 MHz, or a much higher frequency is required to measure the time needed by the wave to transmit and reflect back and get an accurate transmission time, this wave is used for a short distance from 1 cm to 100 cm. However, the generation circuit of such UHF of SHF is structured with very expensive components and is subject to very strict environmental restrictions, therefore, it can not be widely applied to normal situations.